Female terminal fitting for connector

Abstract: A female terminal fitting for a connector comprises: a cylindrical insertion portion whose front end is opened; and a resilient contact piece is disposed within the cylindrical insertion portion. The resilient contact piece includes: a first fold being formed by extending an extending end portion from a wall portion of the cylindrical insertion portion and folding the extending end portion back into a hollow of the cylindrical insertion portion, the first fold being given resiliency; a second fold being formed by further folding the extending end portion inward, the second fold being given resiliency; and a stopper for regulating an amount of flexion of the resilient contact piece, the stopper being formed by bending the extending end portion of the second fold so as to confront a back surface between the first fold and the second fold. A male terminal fitting is retained in pressure contact with the resilient contact piece by inserting the male terminal fitting into the cylindrical insertion portion.

Description: The present invention relates to a connector comprising a male and a female terminal fitting, said female terminal fitting having a cylindrical insertion portion whose front end is opened and which can be connected to the mating male terminal fitting by allowing the male terminal fitting to be inserted into the cylindrical insertion portion. A connector adapted for use in connecting electrical wires is designed to attach a male terminal fitting to one of a pair of connectors to be connected to each other and a female terminal fitting to the other, and to insert the male terminal fitting to a cylindrical insertion portion of the female terminal fitting formed by opening the front end of the female terminal fitting, so that both male and female terminal fittings can be connected to each other electrically. The female terminal fitting has a cylindrical insertion portion formed by bending a metal strip in cylindrical form and a fold formed by folding a part of the metal strip from the front end opening of the cylindrical insertion portion toward the hollow so as to depict a loose arc. A resilient contact piece that is given resiliency is disposed on the fold. One known example is a device shown in Figs. 3 and 4 which is disclosed in JP-A-63-26979, and another one is shown in Fig. 5. Each of these female terminal fittings 50 is constructed so that a resilient contact piece 53 extends rearward by folding the slenderly extending resilient contact piece 53 from the front end opening 52 of a cylindrical insertion portion 51 into the hollow, and causes a not shown male terminal fitting to come in contact with the female terminal fitting by clamping the male terminal fitting between the cylindrical insertion portion 51 and an inner wall 54 thereof by resiliency of the resilient contact piece 53. FR-A-2 415 890 discloses a female connector and according to Figs. 2 and 5 of this document there is provided a resilient contact piece with a first fold, a second fold protruding out of the cylindrical portion and a stopper. Said stopper is not for regulating the flexion of the resilient contact piece such that an over-flexing of this contact piece is prevented. Instead, upon insertion of a male terminal the contact piece is pressed down and abutts at the stopper, so that the cantilevered contact piece becomes supported at two ends, i.e. by the stopper on the one end and the fold at the other end, so that the elasticity of the contact piece is decreased and the contact force is increased. In other words, the contact piece always contacts the stopper upon insertion of the correctly dimensioned male terminal. Provided that an over-dimensioned male terminal or a screw driver or the like is inserted, the contact piece again will rest on the stopper, but since the contact piece also rests on the stopper upon insertion of a regular male terminal, insertion of an over-dimensioned terminal will result in over-bending of the contact piece. Further, as shown in Fig. 6, another example, which is characterized as arranging a second fold 57 formed by folding the front end of the resilient contact piece 53 so as to depict a loose arc, is known. Examples of such known connectors are disclosed in GB-A-1 584 571 and JP-U-2-117672. The present invention starts from the latter known connector in the preamble of claim 1. Exhibiting resiliancy not only at a first fold 56 but also at the second fold 57 on the extended end, such doubly folded resilient contact piece 53 has an excellent spring characteristic. That is, the male terminal fitting can be inserted with ease by a small insertion force and, in addition, once the male terminal fitting has been inserted, the contact pressure is so high as to ensure excellent contact reliability. The resilient contact piece 53 is given resiliency by bending a metal strip. Therefore, if a flexing force exceeding the limit of resiliency is applied to the resilient contact piece 53, i.e., if a foreign object that is thicker than the male terminal fitting (e.g. the tip of a screwdriver) is inserted, or if the male terminal fitting is inserted obliguely, the resilient contact piece 53 settles to loose the proper spring characteristic thereof. To prevent such settling, a stopper has heretofore been arranged on the resilient contact piece 53. In the female terminal fitting shown in Fig. 4, stoppers 60 formed by bending projecting pieces arranged on both sides of the resilient contact piece 53 perpendicularly are provided. The lower end portions thereof are abutted against the bottom surface of the cylindrical insertion portion. The female terminal fitting shown in Fig. 5 has a stopper 61 that is prepared by forming a projection while cutting a part of the wall portion facing the back of the resilient contact piece 53 and bending such projection upward 60 as to correspond to the back of the resilient contact piece 53. Another conventional terminal fitting of this type having, as shown in Fig. 7, a cylindrical contact portion 101 at the front part thereof and a crimping portion 102 for crimping an electrical wire at the rear part thereof has heretofore been known. This terminal fitting is formed cubically by first cutting a developed blank out of a flat metal strip and then bending portions of such developed blank as necessary. A bottom wall 103 of the contact portion 1 is formed by cutting with a band-like metal piece left in the front and by bending the rear end thereof upward, so that the band-like metal piece forms a flexible tongue piece 4 that projects from the bottom wall side to the ceiling wall side within the cylinder. The flexible tongue piece 104 is designed to cause a male terminal fitting to be biased onto the ceiling wall when the male terminal fitting is inserted into the cylinder. On the other hand, a reinforcing piece 105 that is formed by cutting the middle portion of the bottom wall 101 and bending the cut piece upward is designed to prevent the flexible tongue piece 104 from flexing excessively downward. Still further, another conventional female terminal fitting for a connector which is attached to the connector and connected to a male terminal fitting of a mating connector is shown in Fig. 8. This female terminal fitting 340 is fabricated by bending a metal strip piece punched into a predetermined shape, and has a cylindrical insertion portion 341 whose front end is opened serving as an insertion opening 342. A resilient contact piece 345 is disposed within the cylindrical insertion portion 341. The resilient contact piece 345 is given resiliency by a fold 345a with a portion slenderly extending from the front end of a lower wall plate 343 constituting the cylindrical insertion portion 341 folded rearward. The thus constructed female terminal fitting 340 is inserted into a cavity 351 formed in a connector 350 from the rear and unreleasably attached to the connector 350 by a lance 353 with an insertion opening 342 thereof aligned with a connecting opening 352 formed at the front end of the connector 350. At the time the female terminal fitting 340 attached to the connector 350 is connected to the male terminal fitting attached to the mating connector (not shown), a tab 355 projecting from the front end of the male terminal fitting enters into the cylindrical insertion portion 341 while sequentially passing through the connecting opening 352 and the insertion opening 342 of the female terminal fitting. Then, the tab 355 is then clamped between the upper surface of the resilient contact piece 345 and the upper wall surface 346 of the cylindrical insertion portion 341, both surfaces as viewed in Fig. 8, by resiliency of the resilient contact piece 345. As a result, the male terminal fitting is reliably connected electrically to the female terminal fitting 340. In the aforementioned connecting means the connecting opening 352 of the connector 350 has so large an opening as to allow the tab 355 of the male terminal fitting to be releasably inserted, whereas the insertion opening 342 of the cylindrical insertion portion 341 has an opening larger than that of the connecting opening 352 so as to be opened over almost all the front end surface of the cylindrical insertion portion 341. As a result, a foreign object such as, e.g., the tip of a screwdriver which is thicker than the tab 355 may, in some cases, be inserted into the cylindrical insertion portion 341 from the connecting opening 352, or the tab 355 may be inserted obliquely as shown in Fig. 8. In such a sase, the fold 345a of the resilient contact piece 345 flexes to such a degree as to exceed the limit of resiliency thereof and settling occurs due to such excessive flexion, so that the proper spring characteristic of the resilient contact piece 345 is lost. Once the proper spring characteristic has been lost, the resilient contact piece 345 cannot clamp the inserted tab 355 together with the upper wall surface 346 at a predetermined contact pressure, thus not providing reliable contact between the male terminal fitting and the female terminal fitting 340. To prevent the resilient contact piece 345 from loosing the proper spring characteristic thereof, a stopper 348 has conventionally been provided. The front end of the stopper 348 is formed so as to confront the lower surface of the resilient contact piece 345 by bending a part of the lower wall plate 343 of the cylindrical insertion portion 341 upward. This stopper 348 prevents excessive flexion of the resilient contact piece 345. That is, when the resilient contact piece 345 resiliently flexes, the lower surface of the resilient contact piece 345 is abutted against the front end of the stopper before the amount of flexion thereof exceeds the limit of resiliency thereof. As a result, resilient deformation of the resilient contact piece 345 more than such limit of resiliency is blocked, thereby preventing the excessive flexion of the resiliant contact piece 345. Hence, the proper spring characteristic of the resilient contact plece 345 1s maintained, and the male terminal fitting can come in contact with the female terminal fitting 340 reliably. In the conventional female terminal fittings, for instance shown in Figs. 3 and 4, the former stoppers 60 project sideways by a bending margin g that is equal to the thickness of the resilient contact piece as shown in Fig. 4 . Therefore, it is required that the width of the resilient contact piece 53 be smaller at least by a bending margin 2g within the limited width of the cylindrical insertion portion, and this in turn prevents the resilient contact piece 53 from havinq a large resiliency. If the stopper is bent so as not to project sideways by the bending margin g in Fig. 4, then the stopper must be bent by nicking the resliient contact piece in the width direction by the bending margin g , which also prevents the resilient contact piece 53 from having a large resiliency. As a result, particularly small resilient contact pieces have been useless because of their insufficient resiliency. When the stopper 61 shown in Fig. 5, i.e., the stopper formed by cutting a part of the wall portion is applied to the resilient contact piece 53 that has the first and second folds 56, 57 shown in Fig. 6, the cylindrical insertion portion becomes fragile. Therefore, such design has not been applicable to particularly small resilient contact pieces. Although provided with the reinforcing piece 105, the aforementioned conventional terminal fitting as shown in Fig. 7 is deformed when the force biasing the flexible tongue piece 104 is so large. As a result, the flexible tongue piece 104 flexes so excessively as to loose the spring characteristic thereof. In addition, the reinforcing piece 105 is displaced due to a return ensuing the machining operation when formed by cutting and bending upward, and this makes it difficult to place the reinforcing piece 105 in correct position during fabrication. Furthermore, the conventional stopper 61 as shown in Fig. 5 is formed by bending the thin plate substantially perpendicularly, so that a biasing force is applied to the plate edge thereof by the resilient contact piece 53 As a result, when a large biasing force is applied to the stopper 61, the stopper 61 may, in some cases, be so inclined as to loose the function thereof. Particularly, small-sized female terminal fittings have addressed the problem that the stopper thereof ks easily inclined, because the material of which the stopper is made is thin. The conventional method of blocking the excessive flexion of the resilient contact piece 345 by arranging the stopper 348 also has addreased the following problems. When a foreign object is inserted into the cylindrical insertion portion with a large force, the stopper 348 may be broken while inclined by the biasing force from the resilient contact piece 345 side, or the resilient contact piece 345 made of a thin metal plate may be bent. Particularly, small-sized female terminal fittings 340, in which the metal strip used as a material is thin, are easy to cause such problem. As a result, the resilient contact piece 345 is subjected to settling to loose the proper spring characteristic thereof or to hamper smooth insertion. The present invention has been made in consideration of the aforementioned circumstances. The object of the present invention is to provide a connector having a stopper at a doubly folded resilient contact piece, the stopper being capable of preventing settling of the resilient contact piece without loosing the rigidity of a cylindrical insertion portion and the spring characteristic of the resilient contact piece. According to the present invention, there is provided a connector with the features of claim 1. According to the invention, the resilient contact piece formed by extendinq the extending end portion from the wall portion of the cylindrical insertion portion and folding the extending end portion at the first fold has the extending end portion thereof further folded inward at the second fold, so that resiliency is given thereto. Therefore, a male terminal fitting can be inserted into the cylindrical insertion portion at a small insertion pressure, and a high contact pressure is given to the inserted male terminal fitting. Further, the stopper formed by bending the extending end portion of the second fold so as to confront the back surface between the first fold and the second fold. Therefore, even if an excessive biasing force is applied to the first fold, the back surface between the first fold and the second fold is abutted against the stopper so that the stopper regulates the excessive biasing force to an amount of flexion within the limit of resiliency allowed by the first fold. As a result, settling of the resilient contact piece can be prevented. Still further, the stopper is arranged so as to bend the extending end portion of the second fold. Therefore, no such arrangement as nicking the cylindrical insertion portion or the resilient contact piece or narrowing the width of the resilient contact piece is required in order to provide the stopper. As a result, the rigidity of the cylindrical insertion portion and the spring characteristic of the resilient contact piece are not lost. Acording to the invention, when a foreign object such as the tip of a screwdriver which is thicker than the standard male terminal fitting is inserted, the resilient contact piece flexes, and the flexion thereof is supported by the support surface of the stopper within the limit of resiliency of the resilient contact piece. Accordingly, the resilient contact piece is free from flexing to such a degree as to exceed the limit of resiliency thereof to be subjected to settling. In addition, when a large force is applied to the foreign object, the stopper receives the large force through the resilient contact piece. At this time, the stopper, whose rigidity is increased while formed into a U-shaped member by the support pieces at both sides of the support surface, can support the resilient contact piece by the support surface with the support pieces inclined. Therefore, the resilient contact piece can be supported without breaking the stopper. The invention will now be described by reference to the accompanying drawings, in which: Fig. 1 is a partially cutaway side view of a female terminal fitting of the first embodiment; Fig. 2 is a sectional view with a stopper in operation of the female terminal fitting; Fig. 3 is a partially cutaway side view of a conventional example; Fig. 4 is a longitudinal sectional view of the conventional example; Fig. 5 is a partially cutaway side view of the conventional example; Fig. 6 is a longitudinal sectional view of the conventional example; Fig. 7 is a partially cutaway perspective view of another conventional terminal fitting; and Fig. 8 is a sectional view of another conventional example. A first embodiment of the present device will now be described hereinafter with reference to Figs. 1 and 2. A female terminal fitting 1, which is the first embodiment of the present device, is designed to be inserted into a cavity B of a connector housing A and electrically connected to a male terminal fitting while fitted with a tab C of the male terminal fitting attached to a mating connector housing (not shown). The female terminal fitting 1 is formed by punching an electrically conducting metal strip into a predetermined shape and bending the punched blank at predetermined positions. A portion on the front end side constitutes a cylindrical insertion portion 2 that is square in section as a whole. The front end of the portion is open to the outside and serves as an insertion opening 3 of the tab C. A resilient contact piece 10 is disposed within the hollow of the cylindrical insertion portion 2. The resilient contact piece 10 extends from a wall portion 4 on the lower side of Fig. 1 and is integrated with the female terminal fitting 1. The resilient contact piece 10 has a predetermined width that is slightly narrower than that of the hollow of the cylindrical insertion portion 2. The resilient contact piece 10 includes: a first fold 11 folded rearward from the front end edge of the wall portion 4 on the lower side; an extending portion 12 extending from the first fold 11 rearward so as to be slightly obliquely upward and having a contact projection 13 on the way; a second fold 14 formed by bending the extending portion 12 at the end edge thereof downward; and an extending end portion 15 extending from the second fold 14 further frontward. When the resilient contact piece 10 is in a free condition, a gap that is slightly narrower than the thickness of the tab C of the male terminal fitting is provided between the projection 13 of the resilient contact piece 10 and a wall portion 5 of the cylindrical insertion portion 2 on the upper side of Fig. 1. A stopper 16 is provided integrally with the resilient contact piece 10. The stopper 16 is formed by extending the front end of the extending end portion 15 and bending such extending end portion 5 upward. The stopper 16 is almost at right angles to the extending portion 12, and the front end thereof confronts the back (the lower surface) of the extending portion 12 with a predetermined gap when the resilient contact piece 10 is in the free condition. It should be noted that a lance hole 6 is formed on the wall portion 4 on the lower side of Fig. 1 which is in the rear of the resilient contact piece 10 so that a lance D disposed on the connector housing A can be engaged therewith. By engaging the lance D with the lance hole 6 when the female terminal fitting is inserted into the cavity B, the female terminal fitting 1 can be held within the cavity B unreleasably. Further, a core where the coat of the electrical wire (not shown) is stripped is to be firmly secured to a portion 7 in the rear of the cylindrical insertion portion 2. Next, a mode of operation of the first embodiment will be described. When the tab C of the male terminal fitting is inserted into the cylindrical insertion portion 2 of the female terminal fitting 1, and as the tab C advances into the space between the resilient contact piece 10 and the upper wall portion 5 pushingly, the extending portion 12 of the resilient contact portion 10 is pressed down by the tab C. In the meantime, not only the first fold 11 of the resilient contact piece 10 flexes resiliently while increasing the radius of curvature of the bend thereof, but also the front end of the extending end portion 15 is abutted against the lower wall portion 4 to thereby cause the second fold 14 to resiliently flex while increasing the radius of curvature of the bend thereof. Thus, resiliency is applied by both folds, facilitating the male terminal fitting to be inserted at a small insertion pressure, and ensuring highly reliable contact with high contact pressure once the male terminal fitting has been inserted. If the tab C of the male terminal fitting is inserted largely obliquely as shown in Fig. 2, or a foreign object such as the tip of a screwdriver which is thicker than the tab C of the male terminal fitting is inserted into the cylindrical insertion portion 2, a large flexing force is applied to the first fold 11. However, this large flexing force is regulated to a range within which the first fold 11 can be resiliently deformed with the front end of the stopper 16 being abutted against the back of the extending portion 12 within the limit of resiliency of the first fold. As a result, permanent deformation of the resilient contact piece 10 can be prevented. Further, the aforementioned embodiment has thus arranged the stopper 16 so that the stopper 16 is abutted against almost in between the first fold 11 and the second fold 14. Therefore, excessive flexion of not only the first fold 11 but also the second fold 14 can also be regulated. With respect to the condition of the extending end portion 15 at this time, it should be noted that the whole part thereof may come in intimate contact with the lower wall portion 4 as shown in Fig. 2, or only the front end thereof may be abutted against the lower wall portion. In either condition, the stopper 16 similarly blocks the excessive deformation of the resilient contact piece 10. As described above, the stopper 16 regulates the deformation of the resilient contact piece 10 as long as the amount of flexion of both folds 11, 14 of the resilient contact piece 10 is within the limit of resiliency thereof. Therefore, it is no likelihood that the proper spring characteristic of the resilient contact piece 10 will be lost due to settling of the resilient contact piece 10 caused by the resilient contact piece 10 flexing to such a degree as to exceed the limit of resiliency thereof. It should be noted that the present device is not limited to the embodiment that is described above and shown in the drawings, but may be embodied in various modes.

Claims: A connector comprising a male and a female terminal fitting, said female terminal fitting comprising: a cylindrical insertion portion (2) whose front end is open; and a resilient contact piece (10) disposed within said cylindrical insertion portion (2), said resilient contact piece including: a first fold (11) being formed by extending an extending end portion from a wall portion of said cylindrical insertion portion (2) and folding the extending end portion back into a hollow of the cylindrical insertion portion, said first fold (11) being given resiliency, a second fold (14) being formed by further folding the extending end portion inward, said second fold being given resiliency, and a contact projection (13), wherein said male terminal fitting (C) is retained in pressure contact with said resilient contact piece (10) upon correct and complete insertion of said male terminal fitting (C) into said cylindrical insertion portion (2), characterized by a stopper (16) regulating any excessive biasing force to an amount of flexion of said resilient contact piece (10) within the limit of resiliency allowed by the first fold, said stopper being formed by bending the extending end portion of said second fold (14) so as to confront a back surface of said resilient contact piece (10) between said first fold and said second fold, wherein said contact projection (13) is provided between the portion confronting the stopper (16) and the second fold (14), and wherein said stopper (16) and said male terminal fitting (C) being dimensioned such that, upon correct insertion of the male terminal fitting, resiliency is applied by both folds, facilitating the male terminal fitting to be inserted at a small insertion pressure, and ensuring highly reliable contact with high contact pressure once the male terminal fitting has been inserted.

Inventors: AOYAMA MASAHIKO, ITO TOMONARI, OKADA HAJIME, AOYAMA, MASAHIKO, ITO, TOMONARI, OKADA, HAJIME, AOYAMA, MASAHIKO, C/O SUMITOMO WIRINGS SYST. LTD., ITO, TOMONARI, C/O SUMITOMO WIRINGS SYST. LTD., OKADA, HAJIME, C/O SUMITOMO WIRINGS SYSTEMS, LTD.
Applicants: SUMITOMO WIRING SYSTEMS, SUMITOMO WIRING SYSTEMS, LTD.
Application year: 1994
Main classification: H01R13
IPC codes: H01R13